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Radio-frequency discharges are known to operate in two different regimes. The [alpha] regime of low current density and the [gamma] regime with higher current density. Our recent simulation results suggest that the formation of filaments observed in an atmospheric pressure argon discharge under RF excitation could be triggered by the regime transition [alpha] [right arrow] [gamma]. A unidimensional fluid model taking into account the external circuit shows that above 120 mA/[cm.sup.2], the differential conductivity of the discharge becomes negative with a rapid increase in density which can lead to the formation of filaments. As the transition to the [gamma] regime is due to secondary electrons, this threshold value depends on the secondary emission coefficient. In the [gamma] regime, the instantaneous cathode is sustained by secondary electron emission, which drastically changes the behavior of the discharge. In this paper, we present a numerical analysis of the transition between the two regimes and discuss how this could result in the filamentary mode observed in argon RF discharges. Index Terms--Alpha and gamma regime, atmospheric pressure discharges, fluid model, RF discharges, [alpha] [right arrow] [gamma] transition.

The effects of electron-wall interactions on cross magnetic field electron momentum and energy losses in Hall effect thrusters are studied. The results suggest that the electron-wall interactions do not play a very important role in the electron momentum balance in the channel, as the anomalous conductivity is only due to the microturbulence or field fluctuations.

Research describing the analysis of energy loss mechanisms in plasma display panels is presented. In particular neon-xenon discharges are investigated by means of a two-dimensional fluid model.

Research describing the trapping of resonance radiation in plasma display panels is presented. In particular a Monte Carlo model for resonance photons is developed and compared with the traditional fluid model trapping factor method.

Plasma addressed liquid crystal displays are examined.

Atomic rare gas ions are examined.

This work discusses a straightforward way to implement arbitrarily shaped boundaries in fluid models for gas discharges. In most cases using a boundary-fitted numerical grid leads to complicated mathematics. We demonstrate however that it is also possible to represent arbitrarily shaped walls on a uniform grid as grid-fitted boundaries, provided that a correction for diffusional losses is taken into account. Index Terms: Gas discharge displays, gas discharges, modeling.

The electrode evaporation has played a major role in the dynamics of the sheath expansion not only because charged particle transport is no longer collisionless but also because the neutral flow due to evaporation and temperature gradients might push the plasma toward one of the electrodes. Hybrid model of the nonequilibrium postarc plasma and cathode sheath coupled with a direct simulation Monte Carlo method have helped in studying the sheath and plasma dynamics and the time required for the sheath to expel the plasma from the gap for different values of plasma density and electrode temperatures at the beginning of the postarc phase.

The interaction between electromagnetic (EM) fields and hydrogen plasma was investigated in a resonance-type microwave plasma reactor, by combining an elementary theoretical analysis and a self-consistent two-dimensional numerical model. The investigation revealed that the dependence of the reduced field on the gas temperature has a reinforcing effect on plasma formation and may cause jumps in the spatial plasma configuration as a function of power or pressure.

Stationary plasma thrusters (SPTs) are advanced propulsion devices that use a gas discharge to ionize and accelerate the propellant. A 2D hybrid model yields a wide variety of simulation results, depending on the empirical parameters used for anomalous electron transport and energy loss and the model is capable of reproducing experimentally observed SPT behavior and gives interesting insights in the SPT physics.

A two-dimensional model of a stationary plasma thruster (SPT) discharge, which is advanced propulsion devices that use a gas discharge to ionize and accelerate the propellant, is presented. This model is combined with a particle simulation of neutral atoms and ions with a fluid description of electrons, where the electric field is obtained from imposing quasineutrality.

Microdischarges sustained at high gas pressure in specific geometries can be very stable. A particular type of microdischarge, which is the microhollow cathode discharge (MHCD), can be used as an electron source to sustain a larger volume discharge. In this paper, we present results from a numerical study of a microcathode sustained discharge (MCSD) as part of a three-electrode system consisting of an MHCD and an MCSD. The time evolution of the plasma in the MCSD region is shown. Our discussion is focused on the ignition of the MCSD assisted by the electrons coming from the MHCD. Index Terms--Discharge initiation, discharge stability, high-pressure discharge, microcathode sustained discharge, microdischarge, microplasma.

Hall effect thrusters (HETs) are ion sources used for satellite station keeping and orbit raising. In Single Stage HETs, the same electric field is responsible for electron heating and ion acceleration. We present a new HET concept where ionization and acceleration are separated in two different stages. This double stage HET allows for a more versatile operation and a separate control of thrust and specific impulse. Index Terms--Electric propulsion, Hall effect thruster (HET), hybrid model, ion source.

Surface wave discharges (SWDs) are sustained by electromagnetic waves propagating along the plasma surface. We present results of a two-dimensional model, based on the self-consistent numerical solution of Maxwell's equations for the surface wave fields and a set of fluid equations for the plasma, that explain observed effects of the SWD geometry. Index Terms--Electromagnetic propagation in plasma media, plasma simulation, surface wave discharges.